1. Field of the Invention
The present invention relates to a delay amount measuring method of measuring a delay amount in an electronic device that outputs an output signal according to an input signal.
2. Description of Related Art
Conventionally, when measuring a nonlinear characteristic of input and output signals of an electronic device such as an amplifier, the nonlinear characteristic is computed from an amplitude ratio and a phase difference of an input waveform and an output waveform. When such a nonlinear characteristic is computed, it is necessary to accurately match the comparison points of the input waveform and the output waveform. For this reason, it is necessary to accurately measure delay time in an amplifier or the like.
For example, there has been known a method of measuring delay time by means of a cross-correlation function of an input waveform and an output waveform. This method computes a cross-correlation function by performing Fourier transform on the input waveform and the output waveform respectively. Then, a phase characteristic of the cross-correlation function is unwrapped to obtain a characteristic of a straight line, and the delay time is computed from an inclination of the characteristic.
Now, since a related patent document is not recognized, the description is omitted.
However, since a cross-correlation function cannot be computed accurately when nonlinearity in characteristics of an amplifier or the like is strong, delay time in an amplifier or the like cannot be computed with high precision. Moreover, since a phase characteristic of the cross-correlation function is discontinuous even in case of unwrapping the phase characteristic when an input waveform is a discontinuous waveform in a frequency-axis direction, e.g., like a multi-tone signal, delay time in an amplifier or the like cannot be computed with high precision.
When nonlinearity of an amplifier or the like is strong, delay time can accurately be obtained to some extent by obtaining the delay time repeatedly while correcting the nonlinearity. However, there has been a problem that operation time increases extremely and thus measurement efficiency is low. Moreover, since the operation of the phase characteristic is easy to be influenced by a noise or the like, an error may be observed significantly.